The entry level camera that will take the most photos on one charge is probably the:
Fujifilm F10

http://www.dcresource.com/reviews/fuji/finepix_f10-review/

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Your question:

"And what type of batteries consume the least power in a camera"

Of course, batteries do not consume power.
They store power.

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I assume you want to know which type of battery is best to have in your camera.

And the answer is either Lithium or NiMH batteries.

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But how long will a camera last on a particular battery?
Now that is where it gets complicated.

Here are some of the variables involved:
The physical size of the battery.
The voltage of the battery.
How much power can the battery hold
...(measured in Watt Hours or Milliamp Hours)
How much power does it take to run the camera:
...LCD, Lens motor, focus motor, zoom motor, processor, light sensor, prefocus light, etc, etc.

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Camera makers have to consider all those things when designing a camera.

And design is a compromise.
i.e. if you want a small camera, you muct use a small battery.....if you don't, it is no longer a small camera.

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